Year % 1990 15.4929577464789 1991 15.5172413793104 1992 15.8102766798419 1993 15.8273381294964 1994 16.1184210526316 1995 15.9509202453988 1996 16.0112359550562 1997 16.243654822335 1998 16.4383561643836 1999 16.4948453608247 2000 16.4794007490637 2001 16.271186440678 2002 15.919629057187 2003 15.7001414427157 2004 15.5149934810952 2005 15.1990349819059 2006 14.9606299212598 2007 14.6469968387777 2008 14.3422354104847 2009 13.9664804469274 2010 13.556338028169 2011 13.1996658312448 2012 12.8082736674622 2013 12.4620060790274 2014 12.0815138282387 2015 11.6783216783217 2016 11.2382234185733 2017 10.8441558441558 2018 10.4899497487437 2019 10.1034692635423 2020 9.75177304964539 2021 9.48821161587119 2022 9.31919642857143